I'm using a 3d photoshop object in AE for the first time. It's a model of an iPad and I'd like to have a mask on the screen so I can have a comp layer moving beneath it (to look like the content on the ipad screen is being moved or dragged from side to side, etc). However, I can't seem to make a mask on the object work.
You can't make a mask on a 3d object from PSD do what you want it to do.
The one way to try and achieve what you're after is to make a comp the size of the screen and animate the stuff you need inside. Bring that comp in the composition with the 3d PSD object, position it over the screen and link it to the PSD object.
Tudor "Ted" Jelescu
Senior Compositor/VFX Artist